AWS Official Blog

Cross-Region Read Replicas for Amazon RDS for MySQL

by Jeff Barr | on | in Amazon RDS, Amazon Redshift |

You can now create cross-region read replicas for Amazon RDS database instances!

This feature builds upon our existing support for read replicas that reside within the same region as the source database instance. You can now create up to five in-region and cross-region replicas per source with a single API call or a couple of clicks in the AWS Management Console. We are launching with support for version 5.6 of MySQL.

Use Cases
You can use this feature to implement a cross-region disaster recovery model, scale out globally, or migrate an existing database to a new region:

Improve Disaster Recovery – You can operate a read replica in a region different from your master database region. In case of a regional disruption, you can promote the replica to be the new master and keep your business in operation.

Scale Out Globally – If your application has a user base that is spread out all over the planet, you can use Cross Region Read Replicas to serve read queries from an AWS region that is close to the user.

Migration Between Regions – Cross Region Read Replicas make it easy for you to migrate your application from one AWS region to another.  Simply create the replica, ensure that it is current, promote it to be a master database instance, and point your application at it.

You will want to pay attention to replication lag when you implement any of these use cases. You can use Amazon CloudWatch to monitor this important metric, and to raise an alert if it reaches a level that is unacceptably high for your application:

As an example of what you can do with Cross Region Replicas, here’s a global scale-out model. All database updates (green lines) are directed to the database instance in the US East (Northern Virginia) region. All database queries (black lines) are directed to in-region or cross-region read replicas, as appropriate:

Creating Cross-Region Read Replicas
The cross-region replicas are very easy to create. You simply select the desired region (and optional availability zone) in the AWS Management Console:

You can also track the status of each of your read replicas using RDS Database Events.

All data transfers between regions are encrypted using public key encryption. You pay the usual AWS charges for the database instance, the associated storage, and the data transfer between the regions.

Reports from the Field
I know that our users have been looking forward to this feature. Here’s some of the feedback that they have already sent our way:

Isaac Wong is VP of Platform Architecture at Medidata. He told us:

Medidata provides a cloud platform for life science companies to design and run clinical trials faster, cheaper, safer, and smarter. We use Amazon RDS to store mission critical clinical development data and tested many data migration scenarios between Asia and USA with the cross region snapshot feature and found it very simple and cost effective to use and an important step in our business continuity efforts. Our clinical platform is global in scope.  The ability provided by the new Cross Region Read Replica feature to move data closer to the doctors and nurses participating in a trial anywhere in the world to shorten read latencies is awesome. It allows health professionals to focus on patients and not technology. Most importantly, using these cross region replication features, for life critical services in our platform we can insure that we are not affected by regional failure. Using AWS’s simple API’s we can very easily bake configuration and management into our deployment and monitoring systems at Medidata.

Joel Callaway is IT Operations Manager at Zoopla Property Group Ltd. This is what he had to say:

Amazon RDS cross region functionality gives us the ability to copy our data between regions and keep it up to date for disaster recovery purposes with a few automated steps on the AWS Management Console. Our property and housing prices website attracts over 20 million visitors per month and we use Amazon RDS to store business critical data of these visitors. Using the cross region snapshot feature, we already transfer hundreds of GB of data from our primary US-East region to the EU-West every week. Before this feature, it used to take us several days and manual steps to do this on our own. We now look forward to the Cross Region Read Replica feature, which would make it even easier to replicate our data along with our application stack across multiple regions in AWS.

Time to Replicate
This feature is available now and you can start using it today!

You may also want to investigate some of our other cross-region features including EC2 AMI Copy, RDS Snapshot Copy, DynamoDB Data Copy, and Redshift Snapshot Copy.

– Jeff;